Biomass Steam Gasification for Bio-hydrogen Production via Co2 Capture

Abstract

AbstractHydrogen is a promising clean energy carrier for the potential replacement of fossil fuels. Biomass-based hydrogen production is an environmentally sustainable technique that reduces the exploitation of fossil fuel. Catalytic steam gasification is a feasible alternative for producing syngas with a high yield of hydrogen. However, it is associated with producing more carbon dioxide and tar. To address this issue, calcium oxide (CaO) is favoured as a CO2 absorbent which also acts as catalyst for producing H2-rich syngas of high purity (>99%). At lower temperatures (550–650 °C), H2 concentration is greatly improved due to the enhanced absorption effect of CaO, resulting in lower CO and CO2 concentrations; however, at higher temperatures (700–800 °C), CaO works efficiently in cracking pyrolytic volatiles, gasification of char and water gas shift reaction, resulting in higher H2 concentrations. Nevertheless, the challenge of deactivation of CaO after carbonization is overcome by in-situ CaO-based chemical looping. Sorption enhanced reforming technique is an efficient method that integrates tar reforming and in-situ capture of CO2 within the same unit. The chapter gives an overview of enhancing hydrogen concentration in syngas by adapting the CO2 removal technique using CaO.KeywordsBiomass gasificationFluidized bed gasifierCalcium oxide